The Coal Mines Safety Regulations provide that, “live maintenance and movement of electrical equipments, cables and wires are prohibited underground”. However, in practical operations, live maintenance frequently occurs due to a lack of the facilities guarantees, causing countless coal mine accidents. In order to solve this problem, Chinese Patent No. 200710010531.9, titled “Integrative Protection Device and Method for Mineral Grading Lockout Explosion Suppression Vacuum Electromagnetic Starter”, and Chinese Patent No. 200520023343.6, titled “Power-off Upon Cover-Opening Safety Protector for Explosion-Proof Electrical Device”, have proposed two solutions, but both solutions realize automatic power-off upon opening a cover, and cannot cut off the power supply prior to opening a cover.